Closure devices are known comprising a base having a body with a connector portion adapted to mount the closure device on a product container, e.g. by screwing the closure device on the neck of a container or heat- or induction sealing the base to a collapsible pouch.
In known devices the base has a product channel, wherein a rupturable seal is present that spans across the product channel and so occludes the product channel. Examples are shown in WO01/36289. In these examples the closure device includes a protective overcap that is removable by the user upon first opening of the container. Typically an overcap is removable prior to when use of the container is initiated. The overcap is often discarded but may be re-used if desired.